Valves are commonly used to completely or partially stop fluid flow within a system. A wide variety of valves having various sizes, pressure capabilities, and modes of operation are used in conventional systems. As the working fluid pressure is increased, the selection of flow control valves is reduced due to difficult to achieve fluid sealing requirements. As the working fluid pressure is increased to relatively high values, such as 10,000 psi, the valve selection is further reduced and many conventional valves, such as gate valves, butterfly valves, cock valves, globe valves, and ball valves, are inoperable for such relatively high pressures since the fluid sealing requirements become extremely difficult to achieve and due to high stresses created by such high working fluid pressures.
Conventional stem valves and needle valves are often used with such relatively high working fluid pressures. In such stem valves and needle valves, a hardened valve stem is raised or lowered against a fluid passage having a circular cross section, or a circular valve seat. In some conventional valves, the valve stem must be rotated in order to open and close the valve. In other conventional valves, the valve stem slides up and down to open or close a plug within a seat of a fluid passage. Such conventional valve stems extend outside of the valve cavity and are exposed so that suitable forces can be applied to move the valve stem.
Conventional stem valves and needle valves are available for handling fluids at working pressures in excess of 60,000 psi, and are reliable for such service only if the valve stems and needles of such conventional valves, and their mating valve seats, are made of a hardened material which is capable of withstanding high stresses and high fluid friction.
Components of conventional stem valves or needle valves do not move fast enough when the valve is required to operate in an on-off mode. Since such conventional valves are too slow, external forces must be applied to the valve stem so that it slides to quickly open or close the fluid passage. Depending upon the operating conditions, such external force can be applied manually or with power devices. Conventional pneumatic or hydraulic actuators can be used to provide the linear force necessary to push and pull the valve stem. Such actuators use potential energy from compressed air, compressed gas, pressurized oil or another suitable fluid to move a sealed piston having a piston rod connected to the valve stem. Conventional actuator pistons have a surface area considerably larger than the cross-sectional area of the valve stem. With the increased surface area of the actuator piston, much lower pressures can be used to raise or lower the valve stem which is exposed to and acting against the relatively high working fluid pressure. For example, if the valve stem has an outside diameter of 0.25 inches and the fluid pressure inside the valve body is 60,000 psi, the force applied by the fluid to the valve stem is product of the cross-sectional area of the valve stem and the fluid pressure, or 2,940 lb.sub.f. Thus, in order to move the valve stem, a greater force must be applied at the opposite end or actuator end of the valve stem. Also, when the working fluid pressure is relatively high, a frictional force or gripping force is also applied to the valve stem seal assembly. Thus, relatively large sized pneumatic actuators are necessary to provide the force required to move the valve stem. For example, if compressed air is at a pressure of 70 psi, a pneumatic actuator having an air piston of 7.5 inches in diameter is required to translate into a 3,000 lb.sub.f linear force. A pneumatic actuator having an air piston with 7.5 inches in diameter is relatively large, bulky and heavy. Thus, it is apparent that an on-off valve having a valve stem with a relatively small diameter is advantageous since such valve stem requires a smaller actuator when dealing with relatively high working fluid pressures. However, such relatively slim valve stems must be designed to handle stresses involved and thus require high-cost materials, which increases the overall cost of the valve. A valve according to this invention overcomes such disadvantages while maintaining the capability of operating with relatively high working fluid pressures.
Due to recent advances in water jet technology, high water pressures are conventionally available at levels between 10,000 psi to 60,000 psi. In some conventional systems, a manually operated valve is used to control the flow of the high pressure water. Such manually operated conventional valves must handle water pressures up to approximately 35,000 psi. To open and close a fluid port at such high pressure levels requires a high magnitude force that causes fatigue when operated by human hands and the like. The valve according to this invention can be manually operated since such valves are compact, lightweight and relatively easy to operate, even at such very high working fluid pressures.
High pressure water jet operations also require on-off valves which are capable of handling high pressure water at relatively high flow rates. At such relatively high flow rates, the on-off valves are susceptible to shock waves and fluid hammer effects and thus are difficult to design and manufacture. At water pressures of 10,000 psi or greater, quick opening and closing of a relatively large valve port can be very damaging to system components. In such systems, sequential operation of multiple valves with smaller ports is required for safe operation of the system. Sequential operation of multiple valves is common in hydraulic systems. The valve according to one embodiment of this invention is compact and has multiple fluid outlets that are sequentially operated to provide smooth pressure equalization or fluid stoppage. The valve according to this invention can handle such relatively high pressure incompressible fluids at such relatively high flow rates.
In water jet operations, it is also important to regulate water pressure at the discharge of a pump or the water pressure in a piping system. Regulating the pump discharge pressure is also a concern in many other fluid systems. At normal fluid pressures, the system pressure is maintained with conventional fluid pressure regulators. Such conventional pressure regulators vary in design and are basically automatic on-off valves with built-in pressure sensing capabilities to avoid over-pressurization by discharging a certain amount of fluid when necessary. When the fluid is a gas, relieving the pressure is more easily accomplished than when the fluid is a liquid, since only a single opened valve is required to discharge a certain amount of the fluid. However, with incompressible fluids, such as oil and water, the relieving procedure is more difficult, particularly at relatively high pressures. Due to the high pressure, the pressure relief port of a regulator must be either fully opened or fully closed or the valve poppet and valve seat will quickly and severely erode. The flow rate of an incompressible fluid through an orifice is directly related to the cross-sectional area of the orifice. Thus, partial opening of a valve for pressure regulation cannot be applied to incompressible fluids. Conventional single-port pressure regulators for high pressure water applications have many disadvantages, particularly in reliability and sensitivity. Frequent pounding of the valve poppet against a valve seat destroys the seating capabilities within a short period of time. The pressure drop that occurs when a regulator is open is often so great that conventional regulators generate pressure spikes and shocks that damage system components. Also, conventional regulators do not respond to relatively slight pressure variations since they have poor sensitivity to system pressure fluctuations. The valve of this invention is designed to provide an improved, multiple-port pressure regulator which is particularly suitable for use with incompressible fluids at relatively high pressures.
It is thus one object of this invention to provide an on-off valve capable of handling incompressible fluids, such as water and oil, at high pressures in excess of 10,000 psi.
It is another object of this invention to provide an on-off valve which can be operated with reduced forces applied to the valve stem, even at relatively high fluid pressures, with minimum shock effect in a fluid piping system.
It is another object of this invention to provide a pressure regulator compatible with incompressible fluids, such as water and oil, at high pressures with high flow capabilities, reliability and sensitivity.